THE ERA of Good Feeling wasn’t going to last forever at Shea Stadium, everyone understood that. Even Mets fans who harbor the gravest pessimism for their favorite team had difficulty finding much to get upset about.

No, the Mets hadn’t busted out of the gate 35-5 like the ’84 Tigers did – or even 31-11, like the ’86 Mets, for that matter – but they’d won early, won often, built a nice seven-game lead that helped cushion them when the Phillies won all those games in a row.

Best of all, the Mets developed a habit for being an awfully tough out, for finding a way, even in the most improbable games, to get the tying runs on base in the eighth inning, or the tying run to the plate in the ninth. They didn’t always convert those chances, but the heart of a baseball team is in getting into position to win; sometimes, actually winning is in the hands of the game’s many vagaries.

“All you can ask from a team is to be resilient and to keep playing until the game’s over, no matter what the scoreboard says,” manager Willie Randolph said. “I can’t think of a game this year where we haven’t been right there at the end.” Normally, that’s a good thing. Saturday afternoon, however, as the Era of Good Feeling came crashing down around them, the Mets displayed the troubling flip side to that way of life. Because there was no way the middle game of this Subway Series should have been right there at the end. The Mets led 4-0. The Yankees were lifeless. Shea was a combination of Times Square on New Year’s Eve and New Orleans on Mardi Gras.

Until . . .

No need to recount it all here; Mets fans have it already permanently tattooed to the backs of their eyelids, which is why so many of them found sleep so impossible to come by on Saturday night and Sunday morning.

And for the first time all year, Mets fans were filled with an incurable angst.

Angst at the closer, Billy Wagner, for sure, because even a ham-and-egg pitcher should be able to protect a four-run lead in the ninth. But as the hours passed, what rose to the surface was an even angrier reaction to Willie Randolph, to his decision to even bring Wagner into the game in the first place.

Wagner had invited these queries, of course, by refusing to remove his manager from the hook even as he tried to be stand-up about his 31-pitch catastrophe.

Twice he was asked if he was surprised to hear the bullpen phone ring in a non-save situation. Twice he replied, “No comment.” Which was all the fuel most of the faithful needed.

Here’s the thing: Randolph had every right to summon Wagner, especially with an opportunity to lay a hammer down on the Yankees, regardless of how far ahead the Mets were. The Mets need to get back into a habit of winning, that huge cushion in the east has been whittled away, they need to re-establish what they do well.

And nobody will ever convince me or anyone else that the fact that it was the Yankees’ necks that Randolph was trying to step on didn’t play a part. It did. And it should. And from here on out, for as long as he manages the Mets, Randolph can no longer channel Joe Torre and try to minimize these games. Because you can bank on this:

If this were a game against the Marlins, or the Reds, or the Dodgers or the Diamondbacks or the Orioles, Wagner would not have entered the game unless there was some early ninth-inning worries. There are only two teams that, according to Randolph’s own definition of a “crucial series,” he would replicate this strategy – the Braves and the Phillies, the two teams the Mets figure to battle all season for prominence and pre-eminence in the NL East.

The fact that he did it against the Yankees tells you just how important he really thinks these games are. And he should.

Saturday would have been a grand statement victory. He wanted his best to close it. The fact that his best didn’t do that …

well, that happens sometimes. The fact that his best questioned the strategy?